1. Field of the Invention
The present invention relates generally to radio frequency identification (RFID) systems, and more particularly to systems and methods for communications among networked RFID readers to achieve efficient tag interrogations.
2. Background Art
Radio frequency identification (RFID) tags are electronic devices that may be affixed to items whose presence is to be detected and/or monitored.
The presence of an RFID tag, and therefore the presence of the item to which the tag is affixed, may be checked and monitored by devices known as “readers.” Readers typically have one or more antennas transmitting radio frequency signals to which tags respond. Once a reader receives signals back from the tags, the reader passes that information in digital form to a host computer, which decodes and processes the information.
With the maturation of RFID technology, efficient communication between tags and readers has become a key enabler in supply chain management especially in manufacturing, shipping, and retail industries, as well as in building security installations, healthcare facilities, libraries, airports etc.
In some environments, multiple readers may be present. It may be advantageous for a particular group of RFID tags to be interrogated by more than one reader. Various RFID communication protocols enable this functionality. For example, the emerging standardized RFID communication protocol known as Gen 2, allows for RFID tags to be commanded into a number of possible “states,” allowing several readers to interrogate the same tag population.
However, when multiple readers simultaneously send out interrogation signals to an overlapping group of tags, this may cause interference between the interrogation signals. As a result, there may be signal conflict and/or signal degradation, resulting in loss of information. The signal degradation is especially prominent when readers are confined to a fixed frequency or a narrow band of frequency, and have limited number of allowed communication channels.
Thus, what is needed are more efficient and reliable ways for multiple RFID readers to efficiently communicate with RFID tags without unwanted interference.